Axial Capacity Evaluation of Rock-Socketed Cast-In-Situ Concrete Piles

Axial compressive capacity estimations determined from pile load tests (PLTs) are compared with theoretical methods for 13 rock-socketed cast-in-situ concrete piles constructed for different projects in Pakistan. Rock strata encountered at the project sites were mostly shale, siltstone, and sandstone. Rock quality designation (RQD) values fall within 20% to 50%, indicating that the rock mass is in fair to good condition, whereas the rock mass rating system yields a classification of poor to fair. The unconfined compressive strength of the rock cores ranges from 1.5 to 18 MPa. The PLT results show the axial compressive capacities are within 2 and 6 MPa. Axial compressive capacities were also calculated using theoretical methods. An equation is presented to determine the relationship between ultimate capacity and RQD using multiple linear regression analyses. The findings provide useful guidelines for selecting suitable and economical methods for the axial compressive capacities of rock-socketed cast-in-situ concrete piles.